Is it possible to store rigid body cached/baked data into an external folder?
No, there is no option to bake to external cache.

The workaround would be to convert simulation into an Action: Viewport header > Object > Animation > Bake Action (turn visual keying on).



You can store this action in another .blend to link it somewhere later, or in another file format you can import where you like.

If you want to simulate in chunks, you will have to animate the Animated tag under Rigid Body settings to control till which point is the last Action and where the simulation continues.